The teaching in U.S. Pat. No. 9,010,186 improved the detection of detailed transverse fractures over the then existing state of the art. The feature of the invention provides beams (one 0 degree and two 70 degree transducers) tilted from the perpendicular in an amount sufficient to detect detailed fractures which result from longitudinal cracks that propagate in the horizontal plane of the rail.
This feature of the prior art therefore uses both the horizontal and transverse signs of such defects and renders a more robust system, minimizing false alarms due to the 70-degree indication from anomalies such as head checking, surface engine burns and other surface conditions.
The detection of a horizontal component of the detail fracture is only used as defect confirmation in the presence of a transverse component indication from at least one of the 70-degree transducers. The problem of detecting detailed transverse fractures that are in the shadow or masked by the horizontal defects (split head) still exists. This undetected transverse defect component is the predominant cause of service failures and derailments. Currently several detection methods are being introduced to eliminate the horizontal masking affects, some methods include the use single aperture beams reflected off the filet area at the bottom of the rail head upward across and/or toward the top of the rail surface, guided waves, and phased arrays, All have shown limited results and costly to deploy.